On Wed, Jun 18, 2025 at 11:48 AM Anusha Srivatsa <[email protected]> wrote:
> > > On Wed, Jun 18, 2025 at 4:23 AM Maxime Ripard <[email protected]> wrote: > >> On Wed, Jun 18, 2025 at 10:51:58AM +0200, Luca Ceresoli wrote: >> > Hello Anusha, Francesco, >> > >> > On Tue, 17 Jun 2025 11:17:20 -0500 >> > Anusha Srivatsa <[email protected]> wrote: >> > >> > > On Thu, Jun 12, 2025 at 3:24 AM Francesco Dolcini < >> [email protected]> >> > > wrote: >> > > >> > > > Hello all, >> > > > >> > > > Commit de04bb0089a9 ("drm/panel/panel-simple: Use the new >> allocation in >> > > > place of devm_kzalloc()") >> > > > from 6.16-rc1 introduced a regression with this warning during probe >> > > > with panel dpi described in the DT. >> > > > >> > > > A revert solves the issue. >> > > > >> > > > The issue is that connector_type is set to DRM_MODE_CONNECTOR_DPI in >> > > > panel_dpi_probe() that after that change is called after >> > > > devm_drm_panel_alloc(). >> > > > >> > > > I am not sure if there are other implication for this change in the >> call >> > > > ordering, apart the one that triggers this warning. >> > > > >> > > > [ 12.089274] ------------[ cut here ]------------ >> > > > [ 12.089303] WARNING: CPU: 0 PID: 96 at >> > > > drivers/gpu/drm/bridge/panel.c:377 devm_drm_of_get_bridge+0xac/0xb8 >> > > > [ 12.130808] Modules linked in: v4l2_jpeg pwm_imx27(+) imx_vdoa >> > > > gpu_sched panel_simple imx6_media(C) imx_media_common >> > > > (C) videobuf2_dma_contig pwm_bl gpio_keys v4l2_mem2mem fuse ipv6 >> autofs4 >> > > > [ 12.147774] CPU: 0 UID: 0 PID: 96 Comm: kworker/u8:3 Tainted: G >> > > > C 6.16.0-rc1+ #1 PREEMPT >> > > > [ 12.157446] Tainted: [C]=CRAP >> > > > [ 12.160418] Hardware name: Freescale i.MX6 Quad/DualLite (Device >> Tree) >> > > > [ 12.166953] Workqueue: events_unbound deferred_probe_work_func >> > > > [ 12.172805] Call trace: >> > > > [ 12.172815] unwind_backtrace from show_stack+0x10/0x14 >> > > > [ 12.180598] show_stack from dump_stack_lvl+0x68/0x74 >> > > > [ 12.185674] dump_stack_lvl from __warn+0x7c/0xe0 >> > > > [ 12.190407] __warn from warn_slowpath_fmt+0x1b8/0x1c0 >> > > > [ 12.195567] warn_slowpath_fmt from >> devm_drm_of_get_bridge+0xac/0xb8 >> > > > [ 12.201949] devm_drm_of_get_bridge from imx_pd_probe+0x58/0x164 >> > > > [ 12.207976] imx_pd_probe from platform_probe+0x5c/0xb0 >> > > > [ 12.213220] platform_probe from really_probe+0xd0/0x3a4 >> > > > [ 12.218551] really_probe from __driver_probe_device+0x8c/0x1d4 >> > > > [ 12.224486] __driver_probe_device from >> driver_probe_device+0x30/0xc0 >> > > > [ 12.230942] driver_probe_device from >> __device_attach_driver+0x98/0x10c >> > > > [ 12.237572] __device_attach_driver from >> bus_for_each_drv+0x90/0xe4 >> > > > [ 12.243854] bus_for_each_drv from __device_attach+0xa8/0x1c8 >> > > > [ 12.249614] __device_attach from bus_probe_device+0x88/0x8c >> > > > [ 12.255285] bus_probe_device from >> deferred_probe_work_func+0x8c/0xcc >> > > > [ 12.261739] deferred_probe_work_func from >> process_one_work+0x154/0x2dc >> > > > [ 12.268371] process_one_work from worker_thread+0x250/0x3f0 >> > > > [ 12.274043] worker_thread from kthread+0x12c/0x24c >> > > > [ 12.278940] kthread from ret_from_fork+0x14/0x28 >> > > > [ 12.283660] Exception stack(0xd0be9fb0 to 0xd0be9ff8) >> > > > [ 12.288720] 9fa0: 00000000 >> 00000000 >> > > > 00000000 00000000 >> > > > [ 12.296906] 9fc0: 00000000 00000000 00000000 00000000 00000000 >> 00000000 >> > > > 00000000 00000000 >> > > > [ 12.305089] 9fe0: 00000000 00000000 00000000 00000000 00000013 >> 00000000 >> > > > [ 12.312050] ---[ end trace 0000000000000000 ]--- >> > > > >> > > > #regzbot ^introduced: de04bb0089a96cc00d13b12cbf66a088befe3057 >> > > > >> > > > Any advise? >> > > > >> > > > Hey Francesco! >> > > >> > > This mail reached my spam and I hadn't realised till today. Thanks for >> > > bringing this to attention. >> > > >> > > Thinking out loud here: If we called dpi_probe() before allocating the >> > > panel using devm_drm_panel_alloc() >> > > then we would have the connector type. But dpi_probe() needs the >> panel to >> > > be allocated.... >> > >> > Reading the panel-simple.c code, the handling of the panel_dsi >> > descriptor feels a bit hacky, and the recent change to >> > devm_drm_panel_alloc() breaks it easily. Perhaps it would be cleaner to >> > assess the whole descriptor before ding any allocation/init. >> > >> > You're right tat panel_dpi_probe() needs the panel, but it's only at the >> > very end, to assign the descriptor: >> > >> > panel->desc = desc; >> > >> > I think a good fix would be to clean it up by having: >> > >> > * panel_dpi_probe() not take a panel pointer but rather returning a >> > filled descriptor >> > * panel_simple_probe() call panel_dpi_probe() early [before >> > devm_drm_panel_alloc()] and get the filled descriptor >> > * call devm_drm_panel_alloc() with that descriptor in the panel-dsi >> > case, or with the good old descriptor otherwise >> > >> > As a good side effect, it would get rid of a case where >> > devm_drm_panel_alloc() is called with a Unknown connector type. >> > >> > Anusha, does it look like a good plan? >> >> It is, and I'd even go one step further. Like you said, panel_dpi_probe >> kind of exists to allocate and initialize the panel descriptor, and is >> called on the descriptor being equal to the (uninitialized) panel_dpi >> global variable. >> >> We should also get rid of that hack, so do something like creating a >> function that returns the descriptor, and is indeed called first in >> panel_simple_probe. It first calls of_device_get_match_data(), and if >> there's no match, and if the device is compatible with panel-dpi, then >> it calls panel_dpi_probe (we should probably change that name too). That >> way, we can get rid of the panel_dpi variable entirely. >> >> > Thanks Luca and Maxime. > To summarize: > 1. add a function like of_device_get_simple_dsi_match_data() which calls > of_device_get_match_data(). if the device is compatible with panel-dpi, > call > panel-dpi-probe() > 3. Change panel_dpi_probe() to return the panel descriptor > 4. call devm_drm_panel_alloc() > > Looking deeper it looks like I have some gaps in my understanding. panel_simple_platform_probe() already checks of_device_get_match_data() to call panel_simple_probe(). At this point the change suggested is to have to call it again to check if it is compatible with panel-dpi? If I understand correctly panel_dpi is a fallback and the only place the decision to probe panel_dpi() is with the hack. Thanks, > Anusha > >> Maxime >> >
